Faculty of Sport and Health Sciences, Neuromuscular Research Centre, University of Jyväskylä, Viveca 227, Rautpohjankatu 8, 40700, Jyväskylä, Finland.
School of Sport & Exercise, University of Gloucestershire, Gloucester, UK.
Eur J Appl Physiol. 2022 Aug;122(8):1857-1862. doi: 10.1007/s00421-022-04958-8. Epub 2022 May 6.
Measurement of medial gastrocnemius (MG) tendon length using ultrasonography (US) requires the muscle-tendon junction (MTJ) to be located. Previously, the MG MTJ has been tracked from different proximo-distal locations near the MTJ, which could influence estimates of tendon length change due to the different characteristics of the aponeurosis and tendon. We used US to evaluate the effect of tracking point location on MG MTJ displacement during maximal and submaximal (10, 20 and 30% of the non-injured maximal) isometric plantar flexion contractions.
Displacement behaviour of MTJ was tracked from (1) the exact MTJ; and (2) from an insertion point of a muscle fascicle on the aponeurosis 1.3 ± 0.6 cm proximal to the MTJ, in both limbs of patients with unilateral Achilles tendon rupture (ATR) (n = 22, 4 females, 42 ± 9 years, 177 ± 9 cm, 79 ± 10 kg).
In the non-injured limb, displacement (1.3 ± 0.5 cm vs. 1.1 ± 0.6 cm) and strain (6.7 ± 2.8% vs. 5.8 ± 3.3%) during maximal voluntary contraction were larger when tracking a point on the aponeurosis than when tracking the MTJ (both p < 0.001). The same was true for all contraction levels, and both limbs.
Tracking a point on the aponeurosis consistently exaggerates estimates of tendon displacement, and the magnitude of this effect is contraction intensity-dependent. When quantifying displacement and strain of the Achilles tendon, the MTJ should be tracked directly, rather than tracking a surrogate point proximal to the MTJ. The latter method includes part of the aponeurosis, which due to its relative compliance, artificially increases estimates of MTJ displacement and strain.
使用超声（US）测量内侧腓肠肌（MG）肌腱长度需要定位肌-腱结合部（MTJ）。以前，MG MTJ 已经从 MTJ 附近的不同近-远位置进行了追踪，这可能会由于腱旁组织和肌腱的不同特性而影响对肌腱长度变化的估计。我们使用 US 来评估在最大和次最大（非受伤最大的 10、20 和 30%）等长跖屈收缩期间，跟踪点位置对 MG MTJ 位移的影响。
在单侧跟腱断裂（ATR）患者的双侧肢体中，从（1）确切的 MTJ ；和（2）从 MTJ 近端 1.3±0.6cm 处的腱旁组织的一个肌束插入点，追踪 MTJ 的位移行为（n=22，4 名女性，42±9 岁，177±9cm，79±10kg）。
在未受伤的肢体中，在最大自主收缩时，通过腱旁组织上的一个点追踪时的位移（1.3±0.5cm 比 1.1±0.6cm）和应变（6.7±2.8% 比 5.8±3.3%）更大（均 p<0.001）。在所有收缩水平和双侧肢体中均为如此。
通过腱旁组织上的一个点追踪会一致地夸大肌腱位移的估计值，并且这种效果的大小与收缩强度有关。在量化跟腱的位移和应变时，应直接跟踪 MTJ，而不是跟踪 MTJ 近端的替代点。后一种方法包括腱旁组织的一部分，由于其相对顺应性，会人为地增加 MTJ 位移和应变的估计值。
